Improvement in steam-engine slide-valves



\ city and county of San Francisco, and State ol' Gali- 118, 1862, andfor improvementsthereon July 7, 1863.

signed to render the valve of simpler and cheaper con` struction, andmore effective in operation.

`has been closedby the inside lap on the valve, thereby `piston issuddenly driven againstthe air or water, which may be inthe cylinder.

`j `sive friction `on its face, and permit it to be moved lwithsmallexpenditure of power'. i

and steam-chest, and is operated by similar mechanthe `main port isclosed on the exhaust side, I provide `valve, midway between theexhanstcavity and the ,i 1 uitrit tant ANDREW J. s'rnvnNs, or `SANFRANCISCO, CALIFORNIA.

' Letters Patent No. 100,814, dated March. 15,1870; (rn'tella'tedMai-0h45, 1870.

-my w- 1 IMPRovEt/mivr IN STEAM-ENGINE: SLIDE-VALVES."

The Schedule referred to in these LettersrPatent and making part cf thesame.

ll'o `all whom it mag/concern:

Be it known thatI, ANDREW J; STEvnNs'of the fornia, i have inventedcertain new Improvements in my so-called Anti-Coriipression and BalancedSlide- Valve and II d0 hereby declare that the following is a full,clear, and exact description of" the saine, reference being had to theaccompanying drawings and let ters' of reference marked thereon, makinga part of this specilication, in which- Figure 1 is a side view,

z Figure 2 is a cross-section,

Figure 3 is an under-side view, and

Figure 4 is a pla'u or top view ofthe valve.

This invention consists in certain additional Y improvements iny theconstruction and operation of my anti-compression and balancedslide-valve, for which Letters Patent were granted to me, bearing dateJune The additionalI iniprovements I now make are dei First, to releasethe steam,V which may bc in the cylinder on the exhaust side, after theexhanst-port preventing compression by theadvaneing piston.

Second, to relievevthe pressure occurring when the i Third, to partiallyprotect the valve from the pressure of steam on its back, thus torelieve it trom-,exces- 'Io enabl'eotliers skilled in the'art to makeand use my invention I will proceed to describe it as follows:

The main principles of my valve have been described in the previousLettersPatent granted to me,but to make my description of the improvedparts clearly understood, I will here describe the valve complete, andafterward designate what is new and improved.

Myvalvle is in part constructedlike the common slidelvalve,'having samerelations to the cylinder ports ism,' bnt is further provided asfollows:

'Io release the steam remaining in the cylinder when steam passage-waysA A leadingfrom the face of the edge, to the back of thevalve, wherevthey will open into the compartments B B in `the anti-compressionsteam-chamberG. (See iig. 2.) l y Within these compartments BB areprovided the dat valves D D', which alternately open and close acommunication with ythe cent-ral passagewayE,)vl1irh may either lead tothe main exhaust, as shownin dotted lines, iig. 2, or directly to theatmosphere, as shown in same figure. f

The valvesD `D are held apart by the stems F F', which are a triflelonger than the distance between the seats of the valves they divide;thus, when one valve is driven to, the opposite valve will be pushedfrom its seat, and one or other of the steam-passages .will be alwaysopen.

The anti-'compression valve-chamber Otis secured to the back of themain. valve vby the-bolts G G', las

shown in igs. 2 and 4,

The stems F F are not solid with the valves,` but set loosely betweenthem, and are inserted in their positions through holes drilled in theside of the chamber in which they set, which holes are afterward pluggedup by the plugs H H.

The action of this part of my valve is as follows: When, during theoperation of the engine, the main exhaust-passageis closed, and thesteam in the cylinder on the exhausting side lhas not all escaped,compression of the remaining steam, by the advancing piston is avoided,by reason ofthe expanding steam on the steam side closing its ownanti-compression valve, and opening the one corresponding vto theexhausting side, thus a'free exit is provided forthe unexhausted steamthrough, the auxiliary exhausting passages, which connect the main portsin the cylinder with either the exhaust-port or the atmosphere.

Thenext part of my invention-is the provision made for preventing apressure which would be caused by the piston suddenly striking air orwater, which might bein the cylinder. y

lhis is accomplished by what I call the relief. valves I I in connectionwith the steam-passagesA K K'. These steamepassages K K are simplybranches from the anti-compression passages A A'. They are made to leadto the back of the main valve and into the steam-space. v Y Y t Thevalves I I', which open and close these steampassages K K', are connedin the cages L L', which are cast on thefollower M. They are kept totheir seats by the pressure of the steam in the steamechest. There maybe holes l drilled through the `tops of' these cages, to insure thesteam getting at the valve,

if from any cause steam shouldbe prevented from getfiat pieces of metal,

ing steam in the other end of the cylinder. Now, since theanti-compression valve is' only kept open by this steam pressure in theopposite end of the cylinder, then it must be closed when au excessivepressure shall occur in opposition to it. This will often happen whenthe piston drives suddenly against the air or water which may be in thecylinder. At t-his time, my relief-valve will come into' use, for thisexcessive pressure, when greater than the steam pressure which keeps thevalve seated, will raise it up from its seat, open the passage-way, andpermit the air or water to escape into the steam-chest.

With this device, it will be seen that at no time can the pressure inthe cylinder exceed that due to the actual steam pressure.

The last part of my invention is the arrangement for counter-balancingmy valve, and inclosing acornmnnication lwith vthe atmosphere for theescaping steam from the miti-compressionchamber. This consists asfollows:

On the top ofthe main valve, I provide the rim N, which extends aroundthe valve inside of the reliefports'. It is of proportionate height andthickness of metal, as shown in drawing.

Mis a follower, which slips over this rim N down to about a distance asshown in fig. 2.

Tile upper'end of this follower terminates in a broad flange, P, whichbears against the faced surface of the steam-chest cover. 4

I make the joint between the rim N and the follower M steam-tight, bycasting in the angular groove or cavity, which extends around the top ofthe rim N, a ring, R, of soft expansible metal, as type metal. This ringR will be wedge-shaped, with its thin edge set upward, as shown in iig.2. This ring may be cast with the follower in its place;

One or more elliptic springs S, having their ends inserted into cavitiesT in the follower M, and bearing inthe center upon the back of theanti-compression valve-chamber, will serve to keep the follower againstthe surface of the steam-chest cover, when no steam is in thesteam-chest.

There will be two cages L L', as before described, cast on the follower,to inclose the relief-valves I I.

This follower M operates to exclude the steam from the back of thevalve, and thus protects the valve in ameasure from the steam pressure,which would otherwise create a great amount of friction on thevalveface, which would cause a great expenditure of power in operating.

The steam acting against the base of the metal' ring It will wedge itupward and outward tightly against the inside of the follower, and thusinsure a steamtight joint.

The pipe which leads from tbe top of the steamchest cover may eitherlead to the main exhaust-pipe or elsewhere, as desired, or there needonly be an opening left in the steam-chest cover. v

The parts of this invention which are additional improvements on mypreviously-patented valve, and which I desire to have secured to me byLetters Patent of the United States, I will here designate and claim asof my invention as follows: y

1. The improved anti-compression valves D D', being simply long flatvpieces of iron or other metal, in combination with their valve-seatsandthe stems F F', for the purposes as set forth, andconstrueted in themanner substantially as described.

2. The relief-valves I I', in combination ywith their respective cagesand steam-passages K K', for the purposes as set forth, and constructedand arranged in the manner substantially as described.

3. The wedge-shapedmetal ring It, placed inthe cavity around the top ofthe rim N, for the purposes as set forth, and constructed and arrangedin the manner substantially as described.'

ANDREW J. STEVENS.

Witnesses GEORGE PARDY, JAMES L. DRUM.

